Semiconductor device having improved doping profiles and method of improving the doping profiles of a semiconductor device

Abstract

A method of forming the active regions of field effect transistors is proposed. According to the proposed method, shallow implanting profiles for both the halo structures and the source and drain regions can be obtained by carrying out a two-step damaging and amorphizing implantation process. During a first step, the substrate is damaged during a first light ion implantation step and subsequently substantially fully amorphized during a second heavy ion implantation step.

1. A method of amorphizing a crystalline substrate, comprising:
 implanting ions of a first dopant material through a surface of said substrate during a first implantation step so as to produce isolated crystal damage into the substrate to a first predefined depth, wherein during said first implantation step the implanting dose is kept lower than 1×10 14 /cm 2 ; and  
 implanting ions of a second dopant material through the surface of said substrate during a second implantation step so as to substantially amorphize the substrate to a second predefined depth which is less than said first predefined depth, wherein during said second implantation step ions of one of germanium and xenon are implanted.  
 
   
   
     2. The method of  claim 1 , wherein approximately 10% of the crystal damage is produced. 
   
   
     3. The method of  claim 1 , wherein the ions of said first dopant material are lighter than those of said second dopant material. 
   
   
     4. The method of  claim 1 , wherein ions of one of silicon and argon are implanted during said first implantation step. 
   
   
     5. The method of  claim 1 , wherein during said first implantation step the implanting energy is kept higher than 15 keV. 
   
   
     6. The method of  claim 1 , wherein during said second implantation step the implanting energy is kept lower than 150 keV. 
   
   
     7. The method of  claim 1 , wherein during one or both of said first and second implantation steps the substrate is exposed to an ion beam which is kept approximately perpendicular to the surface of said substrate. 
   
   
     8. The method of  claim 1 , wherein during one or both of said first and second implantation steps the substrate is exposed to an ion beam which is kept at a tilt angle with respect to the surface of said substrate. 
   
   
     9. The method of  claim 1 , wherein said substrate contains at least one semiconductive material. 
   
   
     10. A method of forming at least one field effect transistor on a semiconductive substrate, the method comprising:
 forming at least one gate structure above an active region of said at least one transistor;  
 implanting ions of a first dopant material during a first implantation step through the surface of said substrate not covered by said at least one gate structure so as to produce isolated crystal damages into said substrate to a first predefined depth, wherein approximately 10% of the crystal damage is produced; and  
 implanting ions of a second dopant material during a second implantation step through the surface of said substrate not covered by said at latest one gate structure so as to substantially amorphize said substrate to a second predefined depth which is less than said first predefined depth, wherein during said second implantation step ions of one of germanium and xenon are implanted.  
 
   
   
     11. The method of  claim 10 , wherein the ions of said first dopant material are lighter than those of said second dopant material. 
   
   
     12. The method of  claim 10 , wherein ions of one of silicon and argon are implanted during said first implantation step. 
   
   
     13. The method of  claim 10 , wherein during said first implantation step the implanting energy is kept higher than 15 keV. 
   
   
     14. The method of  claim 10 , wherein during said first implantation step the implanting dose is kept lower than 1×10 14 /cm 2 . 
   
   
     15. The method of  claim 10 , wherein during said second implantation step the implanting energy is kept lower than 150 keV. 
   
   
     16. The method of  claim 10 , wherein during one or both of said first and second implantation steps said substrate is exposed to an ion beam which is kept approximately perpendicular to the surface of said substrate. 
   
   
     17. The method of  claim 10 , wherein during one or both of said first and second implantation steps said substrate is exposed to an ion beam which is kept at a tilt angle with respect to the surface of said substrate. 
   
   
     18. The method of  claim 10 , wherein said substrate contains at least one semiconductive material. 
   
   
     19. The method of  claim 17 , wherein said field effect transistor is one of an NMOS, a PMOS and a CMOS transistor. 
   
   
     20. A method of forming at least one field effect transistor on a semiconductive substrate, the method comprising:
 forming a least one polysilicon gate structure above an active region of said at least one transistor;  
 implanting ions of a first dopant material during a first implantation step through the surface of said substrate not covered by said gate structure so as to produce isolated crystal damages into said substrate to a first predefined depth;  
 implanting ions of a first predefined conductivity type during a second implantation step through the surface of said substrate not covered by said gate structure so as to form halo structures into the portions of said substrate containing the crystal damages;  
 implanting ions of a second dopant material during a third implantation step into said halo structures so as to substantially amorphize said substrate to a second predefined depth which is less than said first predefined depth and less than the depth of said halo structures; and  
 implanting ions of a second predefined conductivity type opposed to said first conductivity type during a fourth implantation step into the amorphized substrate.  
 
   
   
     21. The method of  claim 20 , wherein approximately 10% of crystal damages are produced. 
   
   
     22. The method of  claim 20 , wherein the ions of said first dopant material are lighter than those of said second dopant material. 
   
   
     23. The method of  claim 20 , wherein ions of one of silicon and argon are implanted during said first implantation step. 
   
   
     24. The method of  claim 20 , wherein during said first implantation step the implanting energy is kept higher than 15 keV. 
   
   
     25. The method of  claim 20 , wherein during said first implantation step the implanting dose is kept lower than 1×10 4 /cm 2 . 
   
   
     26. The method of  claim 20 , wherein during said third implantation step ions of one of germanium and xenon are implanted. 
   
   
     27. The method of  claim 20 , wherein during said third implantation step the implanting energy is kept lower than 150 keV. 
   
   
     28. The method of  claim 20 , wherein said substrate contains at least one semiconductive material. 
   
   
     29. The method of  claim 20 , wherein said field effect transistor is one of an NMOS, a PMOS and a CMOS transistor. 
   
   
     30. The method of  claim 20 , further comprising forming spacer elements adjacent to a portion of the sidewalls of said gate structure and implanting ions of a predefined conductivity type corresponding to one of said first and second conductivity types during a fifth implantation step through at least the portions of the surface not covered by said gate structure and said spacer elements. 
   
   
     31. The method of  claim 20 , wherein the ions of said first and second conductivity type comprise phosphorous and boron. 
   
   
     32. A method of forming at least one active region in a crystalline substrate, comprising:
 implanting ions of a first dopant material during a first implantation step through at least one portion of the surface of said substrate so as to produce isolated crystal damages into at least one portion of said substrate to a predefined depth;  
 implanting ions of a first predefined conductivity type during a second implantation step through said at least one portion of the surface of said substrate so as to form halo structures into said at least one portion of said substrate containing the damages;  
 implanting ions of a second dopant material during a third implantation step into said halo structures so as to substantially amorphize said substrate to a second predefined depth which is less than said first predefined depth and less than the depth of said halo structures; and  
 implanting ions of a second predefined conductivity type opposed to said first conductivity type during a fourth implantation step into the amorphized substrate.  
 
   
   
     33. The method of  claim 32 , further comprising implanting ions of a predefined conductivity type corresponding to one of said first and second conductivity types during a fifth implantation step through said at least one portion of the surface of said substrate. 
   
   
     34. The method of  claim 32 , wherein approximately 10% of crystal damages are produced. 
   
   
     35. The method of  claim 32 , wherein the ions of said first dopant material are lighter than those of said second dopant material. 
   
   
     36. The method of  claim 32 , wherein ions of one of silicon and argon are implanted during said first implantation step. 
   
   
     37. The method of  claim 32 , wherein during said first implantation step the implanting energy is kept higher than 15 keV. 
   
   
     38. The method of  claim 32 , wherein during said first implantation step the implanting dose is kept lower than 1×10 14 /cm 2 . 
   
   
     39. The method of  claim 32 , wherein during said third implantation step ions of one of germanium and xenon are implanted. 
   
   
     40. The method of  claim 32 , wherein during said third implantation step the implanting energy is kept lower than 150 keV. 
   
   
     41. The method of  claim 32 , wherein said substrate contains at least one semiconductive material. 
   
   
     42. The method of  claim 32 , wherein said field effect transistor is one of an NMOS, a PMOS and a CMOS transistor. 
   
   
     43. The method of  claim 32 , wherein the ions of said first and second conductivity type comprise phosphorous and boron. 
   
   
     44. A method of amorphizing a crystalline substrate, comprising:
 implanting ions of a first dopant material through a surface of said substrate during a first implantation step so as to produce isolated crystal damage into the substrate to a first predefined depth, wherein approximately 10% of the crystal damage is produced; and  
 implanting ions of a second dopant material through the surface of said substrate during a second implantation step so as to substantially amorphize the substrate to a second predefined depth which is less than said first predefined depth.  
 
   
   
     45. A method of amorphizing a crystalline substrate, comprising:
 implanting ions of a first dopant material through a surface of said substrate during a first implantation step so as to produce isolated crystal damage into the substrate to a first predefined depth, wherein during said first implantation step the implanting dose is kept lower than 1×10 14 /cm 2 ; and  
 implanting ions of a second dopant material through the surface of said substrate during a second implantation step so as to substantially amorphize the substrate to a second predefined depth which is less than said first predefined depth.  
 
   
   
     46. A method of amorphizing a crystalline substrate, comprising:
 implanting ions of a first dopant material through a surface of said substrate during a first implantation step so as to produce isolated crystal damage into the substrate to a first predefined depth; and  
 implanting ions of a second dopant material through the surface of said substrate during a second implantation step so as to substantially amorphize the substrate to a second predefined depth which is less than said first predefined depth, wherein during said second implantation step ions of one of germanium and xenon are implanted.  
 
   
   
     47. A method of amorphizing a crystalline substrate, comprising:
 implanting ions of a first dopant material through a surface of said substrate during a first implantation step so as to produce isolated crystal damage into the substrate to a first predefined depth; and  
 implanting ions of a second dopant material through the surface of said substrate during a second implantation step so as to substantially amorphize the substrate to a second predefined depth which is less than said first predefined depth, wherein during one or both of said first and second implantation steps the substrate is exposed to an ion beam which is kept approximately perpendicular to the surface of said substrate.  
 
   
   
     48. A method of amorphizing a crystalline substrate, comprising:
 implanting ions of a first dopant material through a surface of said substrate during a first implantation step so as to produce isolated crystal damage into the substrate to a first predefined depth; and  
 implanting ions of a second dopant material through the surface of said substrate during a second implantation step so as to substantially amorphize the substrate to a second predefined depth which is less than said first predefined depth, wherein during one or both of said first and second implantation steps the substrate is exposed to an ion beam which is kept at a tilt angle with respect to the surface of said substrate.  
 
   
   
     49. A method of forming at least one field effect transistor on a semiconductive substrate, the method comprising:
 forming at least one gate structure above an active region of said at least one transistor;  
 implanting ions of a first dopant material during a first implantation step through the surface of said substrate not covered by said at least one gate structure so as to produce isolated crystal damages into said substrate to a first predefined depth, wherein approximately 10% of the crystal damage is produced; and  
 implanting ions of a second dopant material during a second implantation step through the surface of said substrate not covered by said at latest one gate structure so as to substantially amorphize said substrate to a second predefined depth which is less than said first predefined depth.  
 
   
   
     50. A method of forming at least one field effect transistor on a semiconductive substrate, the method comprising:
 forming at least one gate structure above an active region of said at least one transistor;  
 implanting ions of a first dopant material during a first implantation step through the surface of said substrate not covered by said at least one gate structure so as to produce isolated crystal damages into said substrate to a first predefined depth, wherein during said first implantation step the implanting dose is kept lower than 1×10 14 /cm 2 ; and  
 implanting ions of a second dopant material during a second implantation step through the surface of said substrate not covered by said at latest one gate structure so as to substantially amorphize said substrate to a second predefined depth which is less than said first predefined depth.  
 
   
   
     51. A method of forming at least one field effect transistor on a semiconductive substrate, the method comprising:
 forming at least one gate structure above an active region of said at least one transistor;  
 implanting ions of a first dopant material during a first implantation step through the surface of said substrate not covered by said at least one gate structure so as to produce isolated crystal damages into said substrate to a first predefined depth; and  
 implanting ions of a second dopant material during a second implantation step through the surface of said substrate not covered by said at latest one gate structure so as to substantially amorphize said substrate to a second predefined depth which is less than said first predefined depth, wherein during said second implantation step ions of one of germanium and xenon are implanted.  
 
   
   
     52. A method of forming at least one field effect transistor on a semiconductive substrate, the method comprising:
 forming at least one gate structure above an active region of said at least one transistor;  
 implanting ions of a first dopant material during a first implantation step through the surface of said substrate not covered by said at least one gate structure so as to produce isolated crystal damages into said substrate to a first predefined depth; and  
 implanting ions of a second dopant material during a second implantation step through the surface of said substrate not covered by said at latest one gate structure so as to substantially amorphize said substrate to a second predefined depth which is less than said first predefined depth, wherein during one or both of said first and second implantation steps said substrate is exposed to an ion beam which is kept approximately perpendicular to the surface of said substrate.  
 
   
   
     53. A method of forming at least one field effect transistor on a semiconductive substrate, the method comprising:
 forming at least one gate structure above an active region of said at least one transistor;  
 implanting ions of a first dopant material during a first implantation step through the surface of said substrate not covered by said at least one gate structure so as to produce isolated crystal damages into said substrate to a first predefined depth; and  
 implanting ions of a second dopant material during a second implantation step through the surface of said substrate not covered by said at latest one gate structure so as to substantially amorphize said substrate to a second predefined depth which is less than said first predefined depth, wherein during one or both of said first and second implantation steps said substrate is exposed to an ion beam which is kept at a tilt angle with respect to the surface of said substrate.  
 
   
   
     54. A method of amorphizing a crystalline substrate, comprising:
 implanting ions of a first dopant material through a surface of said substrate during a first implantation step so as to produce isolated crystal damage into the substrate to a first predefined depth, wherein approximately 10% of the crystal damage is produced; and  
 implanting ions of a second dopant material through the surface of said substrate during a second implantation step so as to substantially amorphize the substrate to a second predefined depth which is less than said first predefined depth, wherein during said second implantation step ions of one of germanium and xenon are implanted.  
 
   
   
     55. A method of forming at least one field effect transistor on a semiconductive substrate, the method comprising:
 forming at least one gate structure above an active region of said at least one transistor;  
 implanting ions of a first dopant material during a first implantation step through the surface of said substrate not covered by said at least one gate structure so as to produce isolated crystal damages into said substrate to a first predefined depth, wherein during said first implantation step the implanting dose is kept lower than 1×10 14 /cm 2 ; and  
 implanting ions of a second dopant material during a second implantation step through the surface of said substrate not covered by said at latest one gate structure so as to substantially amorphize said substrate to a second predefined depth which is less than said first predefined depth, wherein during said second implantation step ions of one of germanium and xenon are implanted.